This invention relates to a power change-over mechanism of a vehicle for industrial machinery, which permits free change-over between four-wheel drive and two-wheel drive.
First, a conventional power change-over mechanism will be described hereunder referring to FIG. 1. A first driving shaft 1 for driving a front wheel and a second driving shaft 2 for driving a rear wheel are both aligned on the same axis center, and at the same time they have outward splines 3, 4 respectively. A high-speed gear 5 and a low-speed gear 6 fit onto the first and second driving shafts 1, 2 through bearings 7, 7a, and at the same time they have inward splines 8, 9 respectively. An annular power change-over spool 10 has a pair of inward splines 11, 12 and a pair of outward splines 13, 14 and at the same time it provides an annular groove 16 for engagement with a shift fork and spline fits onto the first driving shaft 1 freely slidingly operably in the axial direction.
In case of the four-wheel drive, the spool 10 is shifted rearward to interconnect the low-speed gear 6 through the spool 4 to the first and second shafts 1, 2. Namely, a power transmitted from an engine through a transmission to the low-speed gear 6 is transmitted through the splines 9, 14 to the spool 10, and further transmitted from the spool 10 to the first driving shaft 1 through means of the splines 11, 3 and to the second driving shaft 2 through means of the splines 12, 4.
In case of the two-wheel drive, the spool 10 is shifted forward to interconnect the high-speed gear 5 through the spool 10 to the first driving shaft 1. Namely, the power transmitted from the engine through the transmission to the high-speed gear 5 is transmitted through the splines 8, 13 to the spool 10, and further transmitted from the spool 10 to the first driving shaft 1 through means of the splines 11, 3 to drive the front wheel.
However, in case when the power change-over mechanism is composed of the power change-over annular spool 10 as a member, the following disadvantages will arise at the time of change-over. Generally, in case of power change-over, a power from an engine has previously been cut off by means of a clutch etc. and the change-over operation is done with a vehicle stopped. However, in case of change-over from the two-wheel drive to the four-wheel drive, meshing of gears is under fixed condition because of the driving shaft 1 being interconnected to the front wheel and the driving shaft 2 being interconnected to the rear wheel, so that the spline 12 of the spool 10 would not mesh with spline 4 of the driving shaft 2 to make the change-over from the two-wheel drive into the four-wheel drive impossible.
Further, under a normal four-wheel drive operation, a torsion will be produced between the driving shafts 1, 2 due to slippage of wheel and large contact forces will be generated between the spline 3 of the driving shaft 1 and the spline 11 of the spool 10 and between the spline 4 of the driving shaft 2 and the spline 12 of the spool 10, so that the spool 10 would not slide to make the change-over from the four-wheel drive into the two-wheel drive impossible. For this reason, a change-over from a high-speed into a low-speed or a change-over from a low-speed into a high-speed will naturally become impossible.
An object of this invention is to dissolve the above disadvantages, i.e. to enable change-overs between the four-wheel drive and the two-wheel drive and between a high-speed and a low-speed by only operating a set of spools once even when a vehicle is stopping with the splines of the driving shafts for the front and rear wheels being not meshed each other due to deviation of phases thereof, or with a torsion being produced between the driving shafts of the front and rear wheels.
In order to accomplish the above object in this invention, a spool is divided into two members: an outer peripheral side member having splines meshing freely with splines of a high-speed gear and a low-speed gear and an inner peripheral side member having splines meshing freely with splines of a first driving shaft and a second driving shaft, said both members are spline connected each other relatively movably in the axial direction and at the same time an interlocking stopper mechanism defining said axial movement within a prescribed range is equipped, and an urging means is provided, which urges the outer peripheral side member toward the direction of operation at the time when the outer peripheral side member is operated.